Energy absorbing foams based upon urethane chemistry are known in the art. The early literature generally utilized halocarbon blowing agents (see, e.g., U.S. Pat. No. 3,926,866). A significant number of patents have issued relating to water blown energy absorbing foams based upon polyols ("filled polyols") prepared by polymerizing styrene/acrylonitrile monomer mixtures in polyethers (see, e.g., U.S. Pat. Nos. 4,116,893, 4,190,712, 4,212,954, 4,866,102, 5,216,041 and 5,232,957). Other patented technology describes the use of relatively low molecular weight crosslinkers (see, e.g., U.S. Pat. Nos. 4,282,330, 5,143.941, and 5,167,884) or the use of various polyols, such as ethylene oxide adducts of Mannich condensates (U.S. Pat. No. 4,371,629), alkoxylated toluene diamine (U.S. Pat. No. 4,614,754), or polyols derived from propylene glycol or ethylene diamine (U.S. Pat. No. 5,187,204).
In addition, we are aware of a commercially available system for the production of energy absorbing foam consisting of:
a) 30 parts by weight of a dispersion of a polyhydrazo-dicarbonamide in a relatively high molecular hydroxyl-containing material; PA1 b) 25 parts by weight of a 630 OH number adduct of ethylene diamine and propylene oxide, PA1 c) 30 parts by weight of a 28 OH number adduct of propylene glycol, propylene oxide and ethylene oxide (having a 13% by weight EO tip), PA1 d) 1 part by weight of a silicone surfactant, PA1 e) 6.7 parts by weight of water, PA1 f) 0.1 part by weight of a catalyst for catalyzing the reaction between water and an isocyanate group, and PA1 g) 152 parts of a polymethylene poly(phenyl isocyanate).
While some of the systems noted above have been used commercially, the search continues for systems which will produce energy absorbing foams which will meet a variety of specifications such as Chrysler specification DC-640 for knee impact, and which also meet commercial production processing requirements of 12 second mold closing, 3 minute demold and low molding pressure. "Mold closing" is defined as the time from the start of the introduction of the foamable reactants into the mold until the mold is dosed. "Demold" time is defined as the time from the start of the introduction of the foamable reactants into the mold until the finished part is removed from the mold. "Molding pressure" is defined as the pressure created in the dosed mold by the reacting and gelling reaction mixture and retained internally by the foam if the closed cell content is high.